This invention relates to a floating magnetic head provided in a magnetic disk apparatus.
Conventionally, a magnetic disk apparatus which is used as a peripheral unit of a computer system is installed in a specialized air-conditioned room. Recent technological progress has allowed computers to be reduced in size and weight and, hence, has brought about reductions in manufacturing costs. Such computers are not always placed in such specialized air-conditioned rooms now, and they are sometimes placed in an ordinary environment. There is consequently a possibility of magnetic disk apparatus being placed in an ordinary environment and becoming more affected by ambient temperature and humidity.
If the ambient temperature around a magnetic disk apparatus placed in an ordinary environment rapidly decreases so that water vapor pressure in the magnetic disk apparatus becomes supersaturated which is higher than saturated water vapor pressure, the water vapor in the air is condensed and forms a thin film of water between a magnetic disk used as a recording medium and a magnetic head for writing or reading information or, to be exact, between the magnetic disk and a slider portion of the main body of the magnetic head. As a result, an attraction phenomenon is caused, that is, the slider portion and the surface of the magnetic disk become fixedly attached to each other. If the magnetic disk starts to rotate in this attached state, an excessive force is applied to the support system of the magnetic head. There is therefore a possibility of the magnetic head being broken.
To prevent this phenomenon, a method such as the one disclosed in Japanese Patent Laid-Open No. 61-80574 has been used. In this method, the magnetic head is thermally deformed through electric heating effected in order to reduce the contact area between the magnetic disk and the slider portion and to generate heat in the slider portion.
FIG. 1 is a perspective view showing an example of a floating magnetic head provided in a conventional magnetic disk apparatus as disclosed in Japanese Patent Laid-Open No. 61-80574. FIG. 2 is a cross-sectional view taken along the line II--II of FIG. 1. A floating magnetic head 1A has a magnetic head body 2A in the form of a box called a monolithic head facing a recording surface 1a of a magnetic disk 1. A pair of slider portions 3A are formed on the magnetic head body 2A. The magnetic head body 2A has a side surface 2a which is paralled to the direction in which the magnetic disk 1 rotates, the pair of slider portions 3A each having a floating surface 3a which extends in parallel with the side surfaces 2a and which contacts the recording surface 1a in the vicinity of a side surface 2a, and a pair of grooves 2b which are formed between the slider portions 3A. A recording and reproducing portion 4 for reading data from or writing data on the recording surface 1a is formed on the head body 2A generally at the center thereof. A side electrode 5 is attached to each side surface 2a of the magnetic head body 2A. Short-circuit electrodes 6 which short-circuit the slider portions 3A are disposed in the grooves 2b. The side electrodes 5 are connected to a dc power source 7 which is turned on or off by a switch 8. As shown in FIG. 2, a thin water film 9 is formed between the recording surface 1a of the magnetic disk 1 and the floating surface 3a by the supersaturation of water vapor occurring therebetween when the ambient atmosphere becomes cool.
The operation relating to this magnetic head will be described below. The magnetic disk apparatus starts to perform the process of recording or reproduction when the switch 8 is closed. A current is then supplied from the positive terminal of the power source 7 to one of the side electrodes 5, so that it flows through the corresponding slider portion 3A, the short-circuit electrodes 6 and the other one of the slider portions 3A to the other one of the side electrodes 5, and thereafter returns to the power source 7 through the negative terminal thereof. At this time, heat is generated in the slider portions 3A and in other portions so that the temperature distribution in the magnetic head body 2A becomes non-uniform. In this case, the magnetic head body 2A is heated at the side facing the magnetic disk 1, therefore the floating surface 3a is convexly deformed by arching in the longitudinal direction. This deformation reduces the area of contact between the floating surface 3a and the recording surface 1a. At the same time, moisture condensed on the floating surface 3a is evaporated by the heat generated in the slider portions 3a. Occurrence of an attraction phenomenon is thus avoided.
However, it is necessary to heat the magnetic head body 2A to a considerably high temperature in order to heat and evaporate the water film 9 formed between the floating surface 3a and the recording surface 1a. Water vapor evaporated from the gap between the floating surface 3a and the recording surface 1a cannot easily be released therefrom to the ambient atmosphere around the magnetic disk apparatus. Further, as the operation of electric-power heating for preventing the attraction phenomenon is repeated, residual strains resulting from the heating accumulate in the magnetic head body 2A. There is therefore a possibility of irregularities occurring in the floating surface 3a, though this surface should be flat. If the floating magnetic head 1A having such irregularities is used to perform recording or reproduction on the magnetic recording surface 1a of the magnetic disk 1, there is a possibility of errors occurring in the output.
Since the conventional floating magnetic head has the above-described construction, the magnetic head body 2A should be repeatedly heated in order to prevent occurrence of the attraction phenomenon between the recording surface 1a and the floating surface 3a. Thus, there is a problem of irregularities occurring in the floating surface 3a in the heating and cooling cycles, resulting in reductions in head performance.